Field of the Invention
The present invention relates to a heat pump system for a vehicle, and more particularly, to a heat pump system for a vehicle, which includes a dehumidification line for supplying some of refrigerant circulating a refrigerant circulation line to an evaporator before the refrigerant is introduced into an exterior heat exchanger after passing a first expansion means so as to dehumidify the interior of the vehicle in a heat pump mode, thereby allowing the refrigerant to smoothly flow to the evaporator of a low pressure through the dehumidification line before the refrigerant is introduced into the exterior heat exchanger which has a higher pressure than the evaporator when the interior of the vehicle is dehumidified, and smoothly dehumidifying the inside of the vehicle.
Background Art
In general, an air conditioner for a vehicle includes a cooling system for cooling the interior of the vehicle and a heating system for heating the interior of the vehicle. At an evaporator side of a refrigerant cycle, the cooling system converts air into cold air by heat-exchanging the air passing outside an evaporator with refrigerant flowing inside the evaporator so as to cool the interior of the vehicle. At a heater core side of a cooling water cycle, the heating system convers air into warm air by heat-exchanging the air passing outside the heater core with cooling water flowing inside the heater core so as to heat the interior of the vehicle.
In the meantime, differently from the air conditioner for the vehicle, a heat pump system which can selectively carry out cooling and heating by converting a flow direction of refrigerant using one refrigerant cycle has been applied. For instance, the heat pump system includes two heat exchangers: one being an interior heat exchanger mounted inside an air-conditioning case for heat-exchanging with air blown to the interior of the vehicle; and the other one being an exterior heat exchanger for heat-exchanging outside the air-conditioning case, and a direction-adjustable valve for changing a flow direction of refrigerant. Therefore, according to the flow direction of the refrigerant by the direction-adjustable valve, the interior heat exchanger serves as a heat exchanger for cooling when the cooling mode is operated, and serves as a heat exchanger for heating when the heating mode is operated.
Various kinds of the heat pump system for the vehicle have been proposed, and FIG. 1 illustrates a representative example of the heat pump system for the vehicle.
As shown in FIG. 1, the heat pump system for the vehicle includes: a compressor 30 for compressing and discharging refrigerant; an interior heat exchanger 32 for radiating heat of the refrigerant discharged from the compressor 30; a first expansion valve 34 and a first bypass valve 36 mounted in parallel for selectively passing the refrigerant passing through the interior heat exchanger 32; an exterior heat exchanger 48 for heat-exchanging the refrigerant passing through the first expansion valve 34 or the first bypass valve 36 outdoors; an evaporator 60 for evaporating the refrigerant passing through the exterior heat exchanger 48; an accumulator 62 for dividing the refrigerant passing through the evaporator 60 into a gas-phase refrigerant and a liquid-phase refrigerant; an inside heat exchanger 50 for heat-exchanging refrigerant supplied to the evaporator 60 with refrigerant returning to the compressor 30; a second expansion valve 56 for selectively expanding the refrigerant supplied to the evaporator 60; and a second bypass valve 58 mounted in parallel with the second expansion valve 56 for selectively connecting an outlet side of the exterior heat exchanger 48 and an inlet side of the accumulator 62.
In FIG. 1, the reference numeral 10 designates an air-conditioning case in which the interior heat exchanger 32 and the evaporator 60 are embedded, the reference numeral 12 designates a temperature-adjustable door for controlling a mixed amount of cold air and warm air, and the reference numeral 20 designates a blower mounted at an inlet of the air-conditioning case.
According to the heat pump system having the above structure, when a heat pump mode (heating mode) is operated, the first bypass valve 36 and the second expansion valve 56 are closed, and the first expansion valve 34 and the second bypass valve 58 are opened. Moreover, the temperature-adjustable door 12 is operated as shown in FIG. 1. Accordingly, the refrigerant discharged from the compressor 30 passes through the interior heat exchanger 32, the first expansion valve 34, the exterior heat exchanger 48, a high pressure side 52 of the inside heat exchanger 50, the second bypass valve 58, the accumulator 62, and a low pressure side 54 of the inside heat exchanger 50 in order, and then, is returned to the compressor 30. That is, the interior heat exchanger 32 serves as a heater and the exterior heat exchanger 48 serves as an evaporator.
When an air-conditioning mode (cooling mode) is operated, the first bypass valve 36 and the second expansion valve 56 are opened, and the first expansion valve 34 and the second bypass valve 58 are closed. Furthermore, the temperature-adjustable door 12 closes a passage of the interior heat exchanger 32. Therefore, the refrigerant discharged from the compressor 30 passes through the interior heat exchanger 32, the first bypass valve 36, the exterior heat exchanger 48, the high pressure side 52 of the inside heat exchanger 50, the second expansion valve 56, the evaporator 60, the accumulator 62, and the low pressure side 54 of the inside heat exchanger 50 in order, and then, is returned to the compressor 30. That is, the evaporator 360 serves as an evaporator and the interior heat exchanger 32 closed by the temperature-adjustable door 12 serves as a heater in the same with the heat pump mode.
However, in case of the conventional heat pump system for the vehicle, in the heat pump mode (heating mode), the interior heat exchanger 32 mounted inside the air-conditioning case 10 serves as a heater so as to carry out heating, and the exterior heat exchanger 48 mounted outside the air-conditioning case 10, namely, at the front side of an engine room of the vehicle, serves as an evaporator which exchanges heat with the outdoor air.
In this instance, if temperature of the refrigerant introduced into the exterior heat exchanger 48 is higher than temperature of the outdoor air, in other words, if temperature of the refrigerant is low, the exterior heat exchanger 48 cannot absorb heat from the outdoor air and is deteriorated in heat-exchange efficiency due to frosting on the exterior heat exchanger 48, and hence, the heat pump system is deteriorated in heating performance and efficiency.
In order to solve the above problems, referring to FIG. 2, a heat pump system for a vehicle disclosed in Korean Patent Publication No. 10-2012-0103054 which has been filed by the same inventor as the present invention will be described in brief. The heat pump system for the vehicle includes: a compressor 70 mounted on a refrigerant circulation line 91 for compressing and discharging refrigerant; an interior heat exchanger 71 mounted inside an air-conditioning case 80 and connected with the refrigerant circulation line 91 of an outlet side of the compressor 70 for exchanging heat between air flowing inside the air-conditioning case 80 and the refrigerant discharged from the compressor 70; an evaporator 75 mounted inside the air-conditioning case 80 and connected with the refrigerant circulation line 91 of an inlet side of the compressor 70 for exchanging heat between the air flowing inside the air-conditioning case 80 and the refrigerant supplied to the compressor 70; an exterior heat exchanger 73 mounted outside the air-conditioning case 80 for exchanging heat between the refrigerant circulating through the refrigerant circulation line 91 and the outdoor air; first expansion means 72 mounted on the refrigerant circulation line 91 of an inlet side of the exterior heat exchanger 73 for selectively expanding refrigerant supplied to the exterior heat exchanger 83 according to the air-conditioning mode or the heat pump mode; second expansion means 74 mounted on the refrigerant circulation line 91 of an inlet side of the evaporator 75 for expanding refrigerant supplied to the evaporator 75; a first bypass line 92 mounted for connecting the refrigerant circulation line 91 of the inlet side of the second expansion means 74 and the refrigerant circulation line 91 of the outlet side of the evaporator 75 with each other such that the refrigerant bypasses the second expansion means 74 and the evaporator 75; and a first direction changing valve 90 mounted at a branching point of the first bypass line and the refrigerant circulation line 91 for changing a flow direction of the refrigerant, such that the refrigerant passing the exterior heat exchanger 73 flows to the first bypass line 92 or the second expansion means 74 according to the air-conditioning mode or the heat pump mode.
Moreover, in order to dehumidify the interior of the vehicle in the heat pump mode, a dehumidification line 94 is mounted for connecting the first bypass line 92 and the refrigerant circulation line 91 of the inlet side of the evaporator 75 with each other so as to flow some of the refrigerant flowing in the first bypass line 92 toward the evaporator 75, and an on-off valve 94a is mounted on the dehumidification line 94.
Furthermore, a second bypass line 93 is mounted in such a way that the refrigerant passing the first expansion means 72 bypasses the exterior heat exchanger 73.
Therefore, under the condition that outdoor temperature is below zero or that frosting is generated on the exterior heat exchanger 73, because the refrigerant bypasses the exterior heat exchanger 73 through the second bypass line 93, it minimizes an influence of the outdoor air of low temperature, and additionally, the heat pump system can be operated smoothly and enhance heating performance because recovering waste heat of electronic units through heat feeding means 76.
Additionally, in the heat pump mode, if it is necessary to dehumidify the interior of the vehicle, the on-off valve 94a of the dehumidification line 94 is opened, and then, the refrigerant expanded in the first expansion means 72 flows to the first bypass line 92 through the exterior heat exchanger 73. In this instance, some of the refrigerant flowing to the first bypass line 92 is branched to the dehumidification line 94 and is supplied to the evaporator 75 so as to carry out dehumidification of the interior of the vehicle.
However, the refrigerant expanded in the first expansion means 72 is heat-exchanged with the cold outdoor air and lowers pressure while passing through the exterior heat exchanger 73. Because the evaporator 75 has little refrigerant in the heat pump mode, finally, based on the on-off valve 94a of the dehumidification line 94 of FIG. 2, pressure of an A side becomes lower than pressure of a B side (evaporator), and hence, the refrigerant flowing in the first bypass line 92 in the dehumidification mode does not flow to the evaporator 75 and flows backwardly. Therefore, it is impossible to dehumidify the interior of the vehicle.